The present invention relates to pressure control valves for selectively discharging fuel vapor pressure from a fuel tank during refueling and introducing air into the fuel tank in response to development of vacuum conditions therein. More particularly, the present invention relates to a stageable tank pressure control valve having a primary stage system for venting the fuel tank to a first destination and an optional auxiliary stage system for venting the fuel tank to a second destination.
New fuel vapors are generated during refueling due to splash and agitation of the dispensed fuel, as well as from potential temperature differences between the fuel tank and the dispensed fuel. In addition, as the liquid fuel dispensed at the pump fills the vehicle fuel tank, fuel vapors that are present in the tank and generated during refueling are displaced by liquid fuel. These displaced fuel vapors are moved out of the fuel tank vapor space by the displacing action of the liquid fuel. In many conventional vehicle fuel systems, these displaced vapors are released directly into the atmosphere via the fuel tank filler neck and are a contributing factor to air pollution.
Although some systems are available to capture and store fuel vapors that are displaced and generated in a fuel tank during a typical vehicle refueling operation, many of these systems are complex to assemble, costly to manufacture, and ineffective and/or unreliable in use. Another shortcoming of typical conventional valves is that the discharge capacity of the valve is lower than that capacity necessary to vent the fuel tank properly during refueling because of small size requirements imposed on these pressure valves. Such small size requirements are made necessary by the shortage of available space in the vicinity of the vehicle fuel tank. Inadequate discharge capacity can result in unwanted discharge of fuel vapor to the atmosphere if fuel vapor exits the tank through the filler neck or other outlet because the conventional tank pressure control valve is unable to regulate the discharge of pressurized fuel vapor to a canister or other suitable fuel vapor treatment site properly and in a timely manner.
One object of the present invention is to provide a tank pressure control valve of small size and economical construction that nevertheless is configured to discharge a substantial volume and mass of pressurized fuel vapor from a fuel tank using a minimum of moving parts during development of high vapor pressure in the tank such as occurs during refueling or the like.
Another object of the present invention is to provide a tank pressure control valve having at least two tank venting stages so that one venting path is established between the fuel tank and a first destination (e.g., a vapor treatment site) upon development of a first pressure magnitude in the tank, and another venting path is established between the fuel tank and a second destination (e.g., an auxiliary fuel vapor treatment site) upon further development of a greater second pressure magnitude in the tank.
Yet another object of the present invention is to provide a tank pressure-relief control valve that is configured to close automatically following conclusion of a vehicle refueling activity, yet is also configured to function as a vacuum-relief valve in response to development of subatmospheric pressure in the fuel tank.
In accordance with the present invention, an apparatus is provided for controlling discharge of fuel vapors from a fuel tank during refueling. The apparatus includes means for conducting fuel vapor between the fuel tank and a fuel vapor treatment site situated outside of the fuel tank, means for selectively blocking flow of fuel vapor through the conducting means, and biasing means. The blocking means is operable between a flow-blocking position and a flow-delivery position. The biasing means acts to yieldably bias the blocking means toward its flow-blocking position.
Means is further provided for receiving and using fuel vapor pressure from the fuel tank having a magnitude in excess of a predetermined threshold level to exert an opening force on the blocking means in opposition to the biasinq means. The usinq means defines a venting control chamber in communication with the blocking means. In operation, the blocking means is moved to its flow-delivery position because of containment of fuel vapor pressure in the venting control chamber, thereby permitting discharge of pressurized fuel vapor in the tank to said fuel vapor treatment site through the conducting means.
In preferred embodiments, the venting control chamber is situated outside of the fuel tank and the blocking means extends through the conducting means into the fuel tank and includes means for communicating fuel vapor from the fuel tank to the venting control chamber. The conducting means includes a partition formed to include a venting aperture interconnecting the fuel tank and fuel vapor treatment site in fluid communication. The blocking means further includes an elongated stem having a valve member affixed at one end and a support member affixed at the other end. The valve member is formed to include a central aperture communicating with the fuel tank and the support member is formed to include a central aperture.
The using means includes first and second walls sealably coupled together to define the venting control chamber. Also, the first and second walls are movable relative to one another to permit expansion and contraction of the volume of the venting control chamber. In a preferred embodiment, the support member forms a portion of the second wall.
The biasing means is situated to act between the partition and the support member normally to urge the valve member against the partition closing the venting aperture. The stem is hollow to provide a pressure transmission passage interconnecting the central apertures of the valve member and the support member and terminating in the venting control chamber to define the communicating means.
Also in preferred embodiments, systems are provided for moving the valve member to its closed position at the conclusion of a refueling activity. Means is provided in the fuel tank for blocking introduction of pressurized fuel vapor in the fuel tank into the communicating means to prevent communication of pressurized fuel vapor to the venting control chamber in response to accumulation of fuel in the fuel tank in excess of a predetermined volume. This level-sensing means acts to shut off supply of pressurized fuel vapor to the venting control chamber through the communicating means. Means is also provided for bleeding pressurized fuel vapor from the venting control chamber at a predetermined rate to permit the biasing means to move the support member and the second wall relative to the first wall, thereby contracting the volume of the venting control chamber and urging the venting valve member toward its flow-blocking position.
A stageable tank pressure control valve further includes means for communicating fuel vapor from the conducting means to at least one of the atmosphere and another fuel vapor treatment site, valve means for selectively blocking flow of fuel vapor through the communicating means, and auxiliary biasing means for yieldably biasing the valve means toward its flow-blocking position. The valve means is operable between a flow-blocking position and flow-delivery positions. In addition, control means communicating with the venting control chamber is provided for using fuel vapor pressure in the fuel tank having a magnitude in excess of a greater second predetermined threshold level to exert an opening force on the valve means so that the valve means is moved in opposition to the auxiliary biasing means to its flow-delivery position. Such movement of the valve member permits discharge of pressurized fuel vapor in the tank to another destination such as a fuel vapor treatment site through the conducting means and the communicating means.
One feature of the present invention is the provision of means for using fuel vapor pressure from the fuel tank in a venting control chamber to control the actuation of flow-blocking means to regulate the flow of fuel vapor into and out of the fuel tank. The blocking means is acted upon by a force generated by fuel vapor pressure in the venting control chamber to move the blocking means from its normal flow-blocking position to its flow-delivery position. Thus, by controlling the surface area of that portion of the blocking means exposed to pressure in the venting control chamber, it is possible to control the actuation of the blocking means with great precision.
In addition, the magnitude of the actuation force applied to the blocking means by fuel vapor pressure in the venting control chamber is not affected by the size of the venting aperture closable by the blocking means. Thus, the size of the venting aperture can be enlarged to increase the discharge capacity of the venting assembly without sacrificing reliability or increasing the overall size of the assembly.
Another feature of the present invention is the provision of a two-stage tank pressure control valve having control means communicating with the venting control chamber for using fuel vapor pressure to open an auxiliary valve. preferably, the control valve is set up to open the auxiliary valve whenever the pressure in the venting control chamber rises above the actuation pressure of the blocking means to a second greater pressure. Advantageously, the auxiliary valve can be used to discharge excess fuel vapor to a second destination (e.g., another fuel vapor treatment site) to avoid overloading the capacity of the canister connectable to the fuel tank by actuation of the blocking means.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.